1. Field of the Invention
The present invention relates to a vacuum pump mounting structure for mounting a vacuum pump for use in a vehicle, and, more specifically, to a vacuum pump mounting structure in which a vacuum pump is connected to an axial end portion of a cam shaft of an engine and is configured to be driven by the cam shaft.
2. Description of the Related Art
A vacuum pump has a function of generating a negative pressure with rotation driving force, and the negative pressure is used for engine negative pressure driving parts such as a negative pressure booster device of a brake, and a VSV (Vacuum Switching Valve) for controlling a turbo charger. Recently, a cam shaft is typically used as a rotation driving source of such a vacuum pump. That is, the vacuum pump is connected to the cam shaft, and is driven by the cam shaft. A vacuum pump mounting structure for such a vacuum pump is disclosed in Patent Document 1, for example. In the vacuum pump mounting structure disclosed in Patent Document 1, a timing gear is attached to an axial end portion of the cam shaft, and a timing chain is wound around the timing gear to transmit rotation of a crankshaft of the engine. The timing chain is covered by a cover. The vacuum pump is connected to the cam shaft, but a body of the vacuum pump is attached to the cover covering the timing chain.
Patent Document 1: Japanese Patent Application Publication No. 2009-085119 A
The cam shaft is supported by a cylinder head with a cam housing. For example, the cam housing is attached to the cylinder head so that the cam shaft is pushed toward the cylinder head side against a reaction force of a lash adjuster. The cam housing may be floated by a force from the cam shaft, which leads to vibration and noise. Since the body of the vacuum pump is simply attached to the cover in the vacuum pump mounting structure according to the related art, it is not possible to suppress the vibration and the noise.